Blockage of human arteries is a widespread malady and, as such, represents a significant health concern. Blockages reducing blood flow through the coronary arteries to the heart can cause heart attacks, while blockages reducing blood flow through the arteries to the brain can cause strokes. Similarly, arterial blockages reducing blood flow through arteries to other parts of the body can produce grave consequences in an affected organ or limb.
The build-up of atherosclerotic plaque is a chief cause of blockages, termed stenoses, which reduce blood flow through the arteries. Consequently, several methods have been introduced to alleviate the effects of plaque build-up restricting the artery. One such method is a procedure termed angioplasty, which uses an inflatable device positioned at the stenosis to dilate the artery. A typical angioplasty device is disclosed in U.S. Pat. No. 4,896,669 to Bhate et al. The device of Bhate et al is typical and, like other angioplasty devices, includes an inflatable balloon which is attached to the distal end of a hollow catheter. The proximal end of the catheter is attached to a fluid source. To treat an arterial stenosis, the balloon is introduced into the artery in a deflated state and guided through the artery over a guide wire to a position adjacent the stenosis. Fluid from the fluid source is then infused into the balloon via the catheter to inflate the balloon. As the balloon expands, it presses against the arterial wall in the region of the stenosis, dilating the artery at the stenosis and restoring it to a sufficient size for adequate blood flow. The balloon is then deflated and removed from the artery, thereby completing the treatment.
While effective for dilating blood vessels, angioplasty devices simultaneously traumatize the tissue of the vessel wall. The dilatation procedure can sometimes excessively stress the tissue of the wall, even to the point of tearing it. Dire consequences to the patient such as an acute occlusion or a thrombosis can result. To address this shortcoming, angioplasty devices have been developed which employ a cutting element in cooperation with the balloon to reduce stress on the tissue of the vessel wall.
One particular disadvantage of an angioplasty device which employs a cutting element, however, is that the cutting element can be exposed to surrounding healthy tissue during placement of the device in the blood vessel of a patient, even when the balloon is deflated. As a result, the sharpened cutting element can inadvertently damage healthy tissue with which it comes in contact. Accordingly, the present invention recognizes a need to provide an angioplasty device which effectively employs a cutting element in cooperation with a balloon during a procedure for dilatation of a stenosis, yet protects healthy tissue from damage during placement of the device in a blood vessel to be treated.
It is therefore an object of the present invention to provide an angioplasty device that can dilate a vessel while minimizing trauma to the tissue of the vessel wall by forming stress-relieving incisions therein. Another object of the present invention is to provide an angioplasty device having a sharp cutting element which can be guided into an artery where the stenosis occurs without significantly damaging healthy tissue along its path. Yet another object of the present invention is to provide an angioplasty device that is relatively easy to use and cost-effective to manufacture.